Infection of L-cells by mengovirus or vesicular stomatitis virus results in the inhibition of cellular protein synthesis. The mechanism by which this inhibition takes place is not understood. In the case of vesicular stomatitis virus (VSV), newly synthesized N protein and virion L and NS proteins are necessary for expression of cellular protein synthesis inhibition. Three to five phosphorylated components associate with the 40S ribosomal subunit after infection by VSV. The appearance of these components correlates with the inhibition of cellular protein synthesis. Several experiments are planned for the coming year. (1) The VSV "N" protein will be isolated and added to a protein synthesizing system from L-cells in an attempt to determine if it has any direct effect on the protein synthesis machinery of the cell. (2) Experiments will be carried out to determine if the phosphorylated components found with the 40S subunits are proteins, RNA contaminants, or phospholipids. Also, attempts to ascertain whether the components are specific for VSV infection or are a general consequence of viral infection will be made. (3) Finally, the effect of VSV infection on the ability of polysomes to translate endogenous cellular and viral mRNAs will be tested. Polysomes from uninfected cells and cells infected with mengovirus or VSV for different periods of time will be isolated and their ability to initiate protein synthesis will be tested. If polysomes from infected cells show an altered ability to initiate translation, crude initiation factors from uninfected cells will be added in an attempt to reconstitute the activity. If the activity is reconstituted, attempts will be made to identify the inhibited factor by adding each of the purified initiation factors to the inhibited extract separately.